ABSTRACT The Antitumor Assessment Core provides support for early discovery of effective antitumor agents and therapeutics. The Core provides resources, professional and technical expertise and advisory services related to the evaluation of agents with potential therapeutic activity, and works closely with investigators to establish in vivo mouse models, including Patient Derived Xenograft (PDX) models, for the design and execution of pharmacokinetic, toxicity and in vivo efficacy studies. The Core also determines the best formulation, administration route, and treatment schedule for each new compound, either alone or in combination with other agents. As such, the Core provides a major vehicle to facilitate pre-clinical studies, including GLP-compliant safety toxicology studies in support of IND applications, and is a major contributor to the translational mission of the Center. The Core helps investigators to design, plan, and execute their in vivo experiments, prepare animal protocols and grant applications involving animal studies, and analyze and summarize data for publication and for IND reporting. Importantly, the Core acts as a central coordinator for studies involving support from several Core facilities (including Animal Imaging, Comparative Medicine and Pathology, Tissue Procurement Service, Organic Synthesis, Integrated Genomics, Radiochemistry and Molecular Imaging Probes, and Molecular Cytology) so that studies are carried out properly and in a time- and cost-efficient manner.